Connected: An Internet Encyclopedia
RFC 1123 - 5.4 SMTP REQUIREMENTS SUMMARY

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### 5.4 SMTP REQUIREMENTS SUMMARY

                                                   |          | | | |S| |
                                                   |          | | | |H| |F
                                                   |          | | | |O|M|o
                                                   |          | |S| |U|U|o
                                                   |          | |H| |L|S|t
                                                   |          |M|O| |D|T|n
                                                   |          |U|U|M| | |o
                                                   |          |S|L|A|N|N|t
                                                   |          |T|D|Y|O|O|t
    FEATURE                                        |SECTION   | | | |T|T|e
    -----------------------------------------------|----------|-|-|-|-|-|--
                                                   |          | | | | | |
    RECEIVER-SMTP:                                 |          | | | | | |
      Implement VRFY                               |5.2.3     |x| | | | |
      Implement EXPN                               |5.2.3     | |x| | | |
        EXPN, VRFY configurable                    |5.2.3     | | |x| | |
      Implement SEND, SOML, SAML                   |5.2.4     | | |x| | |
      Verify HELO parameter                        |5.2.5     | | |x| | |
        Refuse message with bad HELO               |5.2.5     | | | | |x|
      Accept explicit src-route syntax in env.     |5.2.6     |x| | | | |
      Support "postmaster"                         |5.2.7     |x| | | | |
      Process RCPT when received (except lists)    |5.2.7     | | |x| | |
          Long delay of RCPT responses             |5.2.7     | | | | |x|
                                                   |          | | | | | |
      Add Received: line                           |5.2.8     |x| | | | |
          Received: line include domain literal    |5.2.8     | |x| | | |
      Change previous Received: line               |5.2.8     | | | | |x|
      Pass Return-Path info (final deliv/gwy)      |5.2.8     |x| | | | |
      Support empty reverse path                   |5.2.9     |x| | | | |
      Send only official reply codes               |5.2.10    | |x| | | |
      Send text from RFC-821 when appropriate      |5.2.10    | |x| | | |
      Delete "." for transparency                  |5.2.11    |x| | | | |
      Accept and recognize self domain literal(s)  |5.2.17    |x| | | | |
                                                   |          | | | | | |
      Error message about error message            |5.3.1     | | | | |x|
      Keep pending listen on SMTP port             |5.3.1.2   | |x| | | |
      Provide limit on recv concurrency            |5.3.1.2   | | |x| | |
      Wait at least 5 mins for next sender cmd     |5.3.2     | |x| | | |
      Avoidable delivery failure after "250 OK"    |5.3.3     | | | | |x|
      Send error notification msg after accept     |5.3.3     |x| | | | |
        Send using null return path                |5.3.3     |x| | | | |
        Send to envelope return path               |5.3.3     | |x| | | |
        Send to null address                       |5.3.3     | | | | |x|
        Strip off explicit src route               |5.3.3     | |x| | | |
      Minimize acceptance delay (RFC-1047)         |5.3.3     |x| | | | |
    -----------------------------------------------|----------|-|-|-|-|-|--
                                                   |          | | | | | |
    SENDER-SMTP:                                   |          | | | | | |
      Canonicalized domain names in MAIL, RCPT     |5.2.2     |x| | | | |
      Implement SEND, SOML, SAML                   |5.2.4     | | |x| | |
      Send valid principal host name in HELO       |5.2.5     |x| | | | |
      Send explicit source route in RCPT TO:       |5.2.6     | | | |x| |
      Use only reply code to determine action      |5.2.10    |x| | | | |
      Use only high digit of reply code when poss. |5.2.10    | |x| | | |
      Add "." for transparency                     |5.2.11    |x| | | | |
                                                   |          | | | | | |
      Retry messages after soft failure            |5.3.1.1   |x| | | | |
        Delay before retry                         |5.3.1.1   |x| | | | |
        Configurable retry parameters              |5.3.1.1   |x| | | | |
        Retry once per each queued dest host       |5.3.1.1   | |x| | | |
      Multiple RCPT's for same DATA                |5.3.1.1   | |x| | | |
      Support multiple concurrent transactions     |5.3.1.1   | | |x| | |
        Provide limit on concurrency               |5.3.1.1   | |x| | | |
                                                   |          | | | | | |
      Timeouts on all activities                   |5.3.1     |x| | | | |
        Per-command timeouts                       |5.3.2     | |x| | | |
        Timeouts easily reconfigurable             |5.3.2     | |x| | | |
        Recommended times                          |5.3.2     | |x| | | |
      Try alternate addr's in order                |5.3.4     |x| | | | |
        Configurable limit on alternate tries      |5.3.4     | | |x| | |
        Try at least two alternates                |5.3.4     | |x| | | |
      Load-split across equal MX alternates        |5.3.4     | |x| | | |
      Use the Domain Name System                   |5.3.5     |x| | | | |
        Support MX records                         |5.3.5     |x| | | | |
        Use WKS records in MX processing           |5.2.12    | | | |x| |
    -----------------------------------------------|----------|-|-|-|-|-|--
                                                   |          | | | | | |
    MAIL FORWARDING:                               |          | | | | | |
      Alter existing header field(s)               |5.2.6     | | | |x| |
      Implement relay function: 821/section 3.6    |5.2.6     | | |x| | |
        If not, deliver to RHS domain              |5.2.6     | |x| | | |
      Interpret 'local-part' of addr               |5.2.16    | | | | |x|
                                                   |          | | | | | |
    MAILING LISTS AND ALIASES                      |          | | | | | |
      Support both                                 |5.3.6     | |x| | | |
      Report mail list error to local admin.       |5.3.6     |x| | | | |
                                                   |          | | | | | |
    MAIL GATEWAYS:                                 |          | | | | | |
      Embed foreign mail route in local-part       |5.2.16    | | |x| | |
      Rewrite header fields when necessary         |5.3.7     | | |x| | |
      Prepend Received: line                       |5.3.7     |x| | | | |
      Change existing Received: line               |5.3.7     | | | | |x|
      Accept full RFC-822 on Internet side         |5.3.7     | |x| | | |
      Act on RFC-822 explicit source route         |5.3.7     | | |x| | |
      Send only valid RFC-822 on Internet side     |5.3.7     |x| | | | |
      Deliver error msgs to envelope addr          |5.3.7     | |x| | | |
      Set env return path from err return addr     |5.3.7     | |x| | | |
                                                   |          | | | | | |
    USER AGENT -- RFC-822                          |          | | | | | |
      Allow user to enter <route> address          |5.2.6     | | | |x| |
      Support RFC-1049 Content Type field          |5.2.13    | | |x| | |
      Use 4-digit years                            |5.2.14    | |x| | | |
      Generate numeric timezones                   |5.2.14    | |x| | | |
      Accept all timezones                         |5.2.14    |x| | | | |
      Use non-num timezones from RFC-822           |5.2.14    |x| | | | |
      Omit phrase before route-addr                |5.2.15    | | |x| | |
      Accept and parse dot.dec. domain literals    |5.2.17    |x| | | | |
      Accept all RFC-822 address formats           |5.2.18    |x| | | | |
      Generate invalid RFC-822 address format      |5.2.18    | | | | |x|
      Fully-qualified domain names in header       |5.2.18    |x| | | | |
      Create explicit src route in header          |5.2.19    | | | |x| |
      Accept explicit src route in header          |5.2.19    |x| | | | |
                                                   |          | | | | | |
    Send/recv at least 64KB messages               |5.3.8     |x| | | | |

Next: 6. SUPPORT SERVICES

Connected: An Internet Encyclopedia
RFC 1123 - 5.4 SMTP REQUIREMENTS SUMMARY